The present invention relates to a process for preparing a stabilized rosin ester having a higher softening point, and a pressure-sensitive adhesive composition and hot-melt composition containing the stabilized rosin ester as a tackifier.
Heretofore, rosin esters have been used as tackifiers for pressure-sensitive adhesives and hot-melt adhesives, or modifiers for rubbers. Rosin esters have also been incorporated into a variety of plastics to improve their properties such as adhesiveness, rigidity, processability and heat sealability. Common rosin esters have a low softening point and are poor in heat resistance and aging resistance. As rosin esters improved in such properties, disproportionated rosin esters and hydrogenated rosin esters are commercially available. However, these rosin esters also do not have a sufficiently high softening point and superior heat resistance and aging resistance. Therefore there is a great demand for a highly stabilized rosin esters having a higher softening point, particularly suitable for use in pressure-sensitive adhesives and hot-melt adhesives.